AIMS: To use the rs1229984 variant associated with alcohol consumption as an instrument for alcohol consumption to test the causality of the association of alcohol consumption with hay fever, asthma, allergic sensitization, and serum total IgE.

PARTICIPANTS: We included a total of 466434 persons aged 15-82 years from 17 population-based studies conducted from 1997-2015.

MEASUREMENTS: The rs1229984 (ADH1B) was genotyped, alcohol consumption, hay fever and asthma were self-reported. Specific and total IgE were measured from serum samples.

FINDINGS: Observational analyses showed that ever-drinking vs. non-drinking, but not amount of alcohol intake, was positively associated with hay fever and inversely associated with asthma but not with allergic sensitization, or serum total IgE. However, Mendelian randomization analyses did not suggest that the observational associations are causal. The causal odds ratio (OR) per genetically assessed unit of alcohol/week was an OR=0.91 (95% confidence interval (CI): 0.81, 1.02; p=0.101) for hay fever, an OR=0.90 (95% CI: 0.79, 1.02; p=0.095) for asthma, an OR=0.97 (95% CI: 0.80, 1.17; p=0.763) for allergic sensitization, and a 4.7% change (95% CI: -5.5%, 14.9%; p=0.366) for total IgE.

CONCLUSIONS: Ever-drinking vs. not drinking was in observational analyses positively associated with hay fever, and negatively associated with asthma. However, the Mendelian randomization results were not consistent with these associations being causal.